The present disclosure relates to a gas turbine engine and, more particularly, to an inner diffuser case of the engine.
Gas turbine engines, such as those that power modern commercial and military aircraft, generally include a compressor to pressurize an airflow, a combustor for burning a hydrocarbon fuel in the presence of the pressurized air, and a turbine to extract energy from the resultant combustion gases. The compressed air from the compressor section passes between stator vanes, then through a diffuser section. The diffuser has an expanding cross sectional area in the direction of the airflow to decrease the velocity and increase the static pressure of the air. This prepares the air for entry into a combustion section at low velocity to permit proper mixing with fuel.
In gas turbine engines of the twin spool type, leakage of high pressure compressor discharge air through a labyrinth seal between a high pressure compressor rear rotor shaft and the diffuser section typically establishes the thrust loads on component parts such as thrust bearings.
This air is also used downstream in the engine for cooling purposes, particularly, the bearing compartment and the high pressure turbine. Air that is cooler than the environment surrounding the bearing compartment, is bled from the mid-stage compressor either through an anti-vortex tube directing the compressor bleed air radially inward to the engine's shaft where it flows axially to the environment surrounding the mid-frame bearing compartment, or externally from the mid high pressure compressor case to the bearing compartment, then used to supply cooling to portions of the high pressure turbine rotor.
The diffuser case generally divides or separates the leaked high pressure compressor discharge air and compressor bleed air from the high pressure compressor discharge air (or core airflow) used for combustion in the combustor section. Due to thermal transients, the diffuser case experiences localized stress points. Such stress points are often located near or at locations where two components attach. Localized stresses can reduce the useful life of the diffuser case and increase maintenance.